Anomalies of Glass Transition: Manifestation in fullerene core polystyrene stars

Segmental dynamics around T_g in the 4- and 6-arm fullerene (C₆₀) core star-like polystyrenes with different preset arm lengths was studied by DSC as compared to that in the linear PS and PS/C₆₀ blend. The anomalies in glass transition behavior were found for the stars including both suppression and facilitation of segmental motion, and pronounced dynamic heterogeneity within a transition range. The results are interpreted in terms of breakdown of intermolecular cooperativity of segmental motions and PS-C₆₀ interactions.This revised version was published online in November 2005 with corrections to the Cover Date.     

Electron paramagnetic resonance spectra of γ-irradiated polycaprolactam

The nature of the saturation is investigated for radicals trapped in a matrix of polycaprolactam. The radicals were generated with the help of a Co⁶⁰ source of -rays by irradiating evacuated samples consisting of fibers of kapron with two different structural modifications: stretched and unstretched. It is shown that, from its behavior, the broadening is intermediate between the homogeneous and inhomogeneous cases. A study was made of the effect of irradiating dosages in the interval from 1.5 Mrad to 200 Mrad on the form of the EPR spectra; as a result, it was established that with increasing dosage the form of the spectrum (quintet) is preserved, but the intensity of the middle component decreases. The saturation factor here is substantially decreased, but this effect manifests itself to different degrees for specimens of different structural modifications: in the case of the stretched fibers it is enormously stronger than in the case of the unstretched fibers. The study of saturation in the case of specimens of the two investigated modifications, subjected to identical irradiation dosages, has shown that the saturation factor is less for radicals trapped in the more ordered matrix (stretched kapron fibers). Some questions about the chemical nature of the radicals are also considered.     

The infrared spectra of N-(dialkylphosphonomethyl)-urethanes

Journal of Applied Spectroscopy -